TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2832 SUBJECT: GRB 041006: GETS Optical Afterglow Observation DATE: 04/11/05 04:25:03 GMT FROM: Kenzo Kinugasa at Gunma Astro. Obs/Japan K. Kinugasa (Gunma Astronomical Observatory) and K. Torii (Osaka U.) report: Starting at 12:50:19 UT on 2004 October 6 (32 minutes after the burst trigger), the sky area of GRB041006 (Galassi, et al. GCN 2770) was observed with the GETS (0.25-m robotic telescope equipped with unfiltered CCD in the Gunma Astronomical Observatory). The observation continued for 6.5 hours and 30-s exposure frames were obtained. We stacked 20 original frames into a single frame and find that the optical afterglow (Da Costa, et al. GCN 2765) is detected in the stacked frames. Between 12:57 and 14:55 UT (mean epoch), we obtained 10 independent measurements and the afterglow faded from Rc=17.8 to Rc=18.7 by using a comparison star from Henden's calibration (GCN 2801). After 15:02 UT, intermittent clouds came to cover the field of view and the afterglow was not detected.